“The Times they are a’changing”. Only in America could a high profile billionaire seek to move into public housing that has just been vacated by an evicted black family.

It is difficult to see big political revolutions in real time. True revolutions happen about once a century and we are in the midst of one right now. For a hundred years, the battlefield was simple: between left and right, poor and rich, blue and white collar. The old left have now become irrelevant because the digital economy has made the labour heartland in coal, steel, and agriculture largely extinct.

The middle class buys capital but sells labour

In its place are the two new extremes of rich and poor – the mega-rich and the broad, reasonably educated middle class struggling to improve their lot. This is why a very wealthy man who is hypocritically prepared to insult women, religions and foreigners is able to get as much traction in the United States as a presidential candidate. Donald Trump is a thin-skinned bully who confuses slogans for policy and takes political debate personally. He is an angry attack dog who speaks to the hopes of the middle class as a force for change.

They want to vote for something different. Life has been too good for the establishment for too long by making them rich on plentiful money and low interest rates, which favours capital over labour. The middle class buys capital but sells labour. They are not lefty socialists, as proved by the failure of Bernie Sanders and Jeremy Corbyn, but they are looking for a cut of the action.

The Brexit vote was a forerunner of this global phenomenon. Brexit was not a vote to leave Europe but a vote for change; a vote against the establishment. A Trump victory will make Brexit look like a Sunday School tea party.

Hillary Clinton attracts a lengthy and long lasting list of enemies because she is the unacceptable face of the establishment - and the left of centre establishment at that. Yet in a position of leadership, she proved to be an extremely successful foreign minister (and how many people over 50 knew what a email server was five years ago?)

Her greatest chance is that Trump implodes by attacking yet another grieving mother and ends up being impeached even before he reaches the ballot paper. The Republicans can ill afford many more embarrassing political gaffes. It may be “Donald being Donald” but a few Trumpisms in the wrong direction could wreck half a century of peaceful diplomacy and world trade freedoms.

My father Peter, Emeritus Professor of Politics at HKU had one great lesson from a lifetime of studying politics. “Democracy is not about voting people in, it is about voting them out.”

The Democrats call Trump a demagogue – a description for those who whip up popular fervour, only to use their popularity as a dictator over the people. It is unlikely that the great American constitution will stand for that, but a classic example in the making is Turkish President Recep Tayyip Erdogan. No one wanted a military government in Turkey but it was possible that they would return to democracy in a few years.

Our future stability rests on just how much unknown change the middle class in the US, France and Germany really want

Erdogan has used the failed coup to enforce a state of emergency, crush freedom of speech, and to imprison potential opponents. He is building domestic support by using Dictator 101 rules of paranoia; accusing the West of being involved, and finding a 75-year old exile to blame. On a personal note, he is willing to disrupt bilateral relations with Italy who are investigating his son for money laundering. It is even an offence to insult him, whatever that is - something no doubt Trump would approve. In that environment, the difference between a criminal and a bookseller becomes very thin. Erdogan is unlikely to go quietly in the next election if the people vote him out. If there is a next election.

In the face of this turmoil, Hong Kong and China appear to be a relative haven of political stability but this will not protect us from revolutions in the political landscape elsewhere. The desire for change allowed dictators in the 1920s and 1930s to be voted in and they remained in power through bullying, xenophobia, nationalism, and aggression.

Such forces will impact relations across the world. Our future stability rests on just how much unknown change the middle class in the US, France and Germany really want – and who is able to capture that mood.